The trends in vehicle design are towards lighter vehicles to improve fuel consumption. At the same time, manufacturers continue to demand more rigorous structural performance standards. The use of lighter hollow cross-sectional members that are used to form a vehicle body has lead to the need for additional reinforcement in various locations in the vehicle body. As is well known, the vehicle body generally undergoes an electrocoat process in which the vehicle body is passed through a bath of anticorrosion fluid whereby an anticorrosion coating is deposited onto the vehicle body by electrolysis. The vehicle body is subsequently heated to bake the coating on the metal. Therefore, it is desirable for that the reinforcement does not prevent the provision of the anticorrosion coating on the inner surface of the hollow member by the electrocoat process.
It is known to provide longitudinal reinforcing structures within the hollow cross-sectional members of the vehicle body. The structure is typically provided with an expandable adhesive on two surfaces, which can be foamed upon heating to bond the beam to two opposed walls of the hollow member. However, this technique is not suitable for use in the electrocoat process described above as it can prevent the proper electrocoat over the entire surface, which can lead to local areas of corrosion. Another known reinforcement includes an aluminum honeycomb for its light weight and high strength. However, it is difficult to isolate the aluminum from the steel hollow member, to correctly position the reinforcement inside the hollow member, and to prevent the anti-corrosion fluid from filling the honeycomb and adding weight. It is also known to provide foamable plastic moldings within the hollow members which can be foamed upon application of heat, such as is provided by the baking step in the electrocoat process, to provide a foamed baffle that fills the cross-section to provide sound adsorption. These inserts can be used to provide acoustic baffles and seals.